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Radiation Biology, Effects and Risk

Radiation Biology, Effects and Risk. Bruce Busby Radiation Safety Manager FHCRC. Introduction. FHCRC Seattle, WA Cancer research – prevention and treatment Established in 1975 Broadscope biomedical research lab 3,000 employees, 600 radiation workers 3 Nobel prize winners.

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Radiation Biology, Effects and Risk

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  1. Radiation Biology, Effects and Risk Bruce Busby Radiation Safety Manager FHCRC

  2. Introduction • FHCRC • Seattle, WA • Cancer research – prevention and treatment • Established in 1975 • Broadscope biomedical research lab • 3,000 employees, 600 radiation workers • 3 Nobel prize winners

  3. Today’s Objective • What today's lecture will do: • Discuss Sources of Radiation • Discuss Radiation Interactions with Humans • Review Basics of Effects of Radiation • Review Risk with Examples

  4. Radiation Physics

  5. Radiation • Radiation: Energy in transit, either as particles or electromagnetic waves • Ionizing Radiation: Radiation with enough energy to cause an electron to leave an atom • 4 main types • Alpha particles • Beta Particles • Neutrons • Gamma and X-ray

  6. Gamma-Ray and Beta Decay  Gamma Rays (317 and 296 keV) Parent Nucleus Ir-192 Daughter Nucleus Pt-192

  7. X-Ray Production (Bremsstrahlung) Electron X-Ray Target Nucleus Tungsten Anode (+) Cathode (-) X-Rays

  8. Gamma/X-ray Interactions • Gamma and X-ray (photons) energy causes excitation or ionization of electrons • Probability of interaction based on electron density and energy of photon • why lead and DU?

  9. Units of Radiation • Exposure and dose can be measured easily, and is expressed using the units of • Roentgen • Rad • Rem • Radioactivity • Curie

  10. Roentgen (R) • Measure of exposure • Charge produced in a specific volume by gamma or x-rays • 1 R = 2.58 x 10-4 C/kg • SI unit is C/kg • Meters (Ion Chambers and GM detectors) often read out in mR/hr

  11. RAD • Radiation Absorbed Dose • Energy deposited per unit mass • 1 rad = 100 erg/gm • Does not account for different radiation damages • SI unit is the gray (Gy) • 100 rad = 1 Gy

  12. REM • Measure of Biological Damage • Effective Dose Equivalent • External or partial body dose (EDE) • Total Body Dose (TEDE) • Internal Dose (CEDE) • rad x QF = rem • QF based on differences in types of radiation • SI unit is sievert (Sv) • 100 rem = 1 Sv

  13. Good News • For x-ray, beta and gamma radiation 1 R  1 rad  1 rem • Bad news is for alpha and neutron, have to take into account the quality factor rad x QF = rem • QF for alpha is 20, neutron 2-20, gamma/beta is 1

  14. Measures of Radioactivity The quantity of radioactive material present at a given time: Curie (Ci) : 3.7x1010 disintegration per second (dps) or Becquerel (Bq): 1 dps

  15. Radiation Sources and Doses

  16. Sources • Natural - Sea of Radiation • Radon • Cosmic • Terrestrial • Human-produced • Nuclear Medicine • Cancer Therapy • Nuclear power

  17. Average US Dose

  18. Factors in Background • Location, location, location • Radon • Cosmic • Terrestrial • Flying • Smoking • X-rays and nuclear medicine • Examples

  19. Sources in Radiography • Ir-192 • Co-60 • X-ray • Other

  20. Ir-192 • Half Life - 73.827 d • Decay modes β95.24% ε 4.76% • Major Gammas • 295 keV 308 keV 316 keV • 468 keV • Made from Ir-191 (n, gamma)

  21. Typical Radiation Doses Flight from Los Angeles to New York 3 mrem Chest X-ray 10 mrem Annual public dose limit 100 mrem Annual background 360 mrem Fetal dose limit (gest. period) 500 mrem Radiographers annual (1993 Value) 540 mrem CT Scan 780 mrem Annual radworker WB dose limit 5,000 mrem Acute radiation syndrome 100,000 mrem LD50/60 for humans 350,000 mrem Radiation therapy 1,200,000 mrem

  22. Radiation Biology

  23. Cells in Your Body • Trillions of cells make up the body • Cells --> Tissue --> Organs -->Body • Active cells are more radio-sensitive • White blood cells, Bone marrow, Stomach lining, Hair follicles • Inactive cells are radio-insensitive • Bone, Muscle, Tendon, Nerves, Skin

  24. Radiation Damage - Ionization • Radiation causes Ions and free radicals in cell ex: Radiation + H20 -> OH- + H• • These free radicals and ions react with parts of the cell • attack sensitive areas • cause damage • May have direct damage to “targets” also

  25. Damage - Cell • Most Critical Target in Cells - DNA • Damage DNA • MAY cause effects to the cell • H2O coating is primary target • Single breaks (SSB) • Double strand breaks (DSB)

  26. Damaged Cells • Once Damaged, the Cell May: • Repair the damage - No problem • Damaged cells held in cell cycle • Enzymes repairs SSB and some DSB • Die - No problem on small basis • 1% of cells die each day • No longer working • Mis-repair/non-repair – BAD • Too many dead cells – BAD

  27. Health Effects • From cell to health effects • Cells --> Tissue --> Organs -->Body • Effects Depends on • dose rate (Acute or Chronic) • dose • type of radiation • location of dose

  28. More Terms - Effects • Stochastic (random) • No known threshold • Cancer • Risk proportional to dose • Non-stochastic (not random) • Have threshold • Cateracts • Burns

  29. Lets Look at the Effects • Whole Body Acute • Partial Body Acute • Whole Body Chronic • Somatic • Heritable

  30. WHOLE BODY ACUTE

  31. Whole body • Effects are based on sensitive tissues • Hematopoietic Syndrome (blood) • Gastrointestinal Syndrome (stomach/intestines) • CNS Syndrome (nerves and brain) • Early Effects • Latent Effects • Late Effects

  32. Effects Based on Dose • Dose 10 rem • no symptoms, no method of detecting outside of dosimeters • Dose ~ 50 rem • no symptoms, minor decreases in white cells and platelets • Dose ~ 75 rem • No symptoms in most people, decrease in white cells

  33. Acute Radiation Syndrome> 100 rem • Early (Prodromal) stage • nausea, vomiting, diarrhea and fatigue • higher doses produce more rapid onset and greater severity • Latent period (Interval) • patient appears to recover • decreases with increasing dose

  34. Acute Radiation Syndrome • Dose ~ 100 rem • ~10% exhibit nausea and vomiting within 48 hr • mildly depressed blood counts • Dose ~ 350 rem • ~90% exhibit nausea/vomiting within 12 hr, 10% exhibit diarrhea within 8 hr • severe bone marrow depression • ~50% mortality without supportive care • Dose ~ 500 rem • ~50% mortality with supportive care • Dose ~ 1000 rem • 90-100% mortality despite supportive care

  35. Acute Radiation Syndrome • Dose ~ 1000 - 3000 rem - damage to GI system • severe nausea, vomiting and diarrhea (within minutes) • short latent period (days to hours) • usually fatal in days to weeks • Dose > 2,000 rem - damage to CNS • vomiting, diarrhea, confusion, severe hypotension within minutes • collapse of cardiovascular and CNS • fatal within 24 to 72 hours

  36. PARTIAL BODY ACUTE

  37. Localized Dose • Local skin and tissue damage • Beyond cellular repair rate • Burns • Dead tissue • Late effects • Typical – hands, fingers, skin, eyes • Other – thigh, rear, chest….

  38. Localized Radiation Effects • Skin - No visible injuries < 500 rem • Prompt - erythema, epilation >600 rem • Moist desquamation >1,800 rem • Ulceration/Necrosis >2,400 rem • Eyes - Cataracts • Acute exposure >200 rem • Chronic exposure >600 rem • Permanent Sterility • Female >250 rem • Male >350 rem

  39. Example -Acute Localized Exposure Day 1: Estimated exposure 22,000 to 30,000 rems to the hands

  40. Day 56 • Damaged tissue can no longer be exposed to air • Padding is needed because touching the areas is extremely painful

  41. 5 Years • Areas ulcerated and refused to heal • Right hand index finger had to be amputated • Hands very sensitive to heat and cold • Further amputation may be necessary

  42. Epilog With a 100 Ci I-192 source in close contact with you, how long would it take to get • 500 rem hand dose • 1500 rem hand dose • 20,000 rem hand dose (10 R whole body) • 2 seconds • 6 seconds • 1 minute

  43. Actions for Acute High Dose WB • Estimating the severity of rad injury is difficult. • Signs and symptoms: Rapid onset and greater severity indicate higher doses. Can be psychosomatic. • CBC with absolute lymphocyte count • Chromosomal analysis of lymphocytes • Treat symptomatically. Prevention and management of infection is the primary objective. • Hematopoietic growth factors, e.g., GM-CSF, G-CSF (24-48 hr) • Antibiotics/reverse isolation • Electrolytes • Seek the guidance of experts. • Radiation Emergency Assistance Center/ Training Site (REAC/TS)

  44. WHOLE BODY CHRONIC

  45. Chronic Health Effects from Radiation • Based on damage to DNA • Cancer is the major risk from low dose radiation • Cancer is also common in humans • Radiation risk is low and natural occurrence of cancer is high • Makes studying low level risk hard • Often extrapolated from high doses to low using a linear relationship

  46. Genetic Effects - heritable • Of the offspring and descendents of the survivors of Nagasaki and Hiroshima (>100,000 people), there have been no observable increase in the mutation rate. • The risk is still possible, though much smaller (10X) than the risk of cancer • Doubling dose in humans is 100 rem

  47. Radiation Risk

  48. Risks • Risk is a personal choice • Weighing benefit • Something we do every day • Needs to be informed • Often bias based on bad information, stereotypes, myths

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